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Before the 1981 Yankees-Dodgers World Series returned to New York for a decisive Game 6, Yankees starter Tommy John told an inquisitive acquaintance about his tired-arm theory.

John, who at 38 would give up only one run in 13 Series innings, explained it like this the morning of Game 3 in Los Angeles: After undergoing his patented ligament-replacement elbow surgery seven years earlier, he had discovered that his repaired left arm was too strong to throw the sinking fastball -- his post-op, career-prolonging pitch. While employed by the Dodgers before his switch to the Yanks in '79, John described toiling in his vegetable garden the day he was due to pitch one night in Chavez Ravine. He pitched exceptionally that night.

Call it a cerebral man's science -- or just another ballplayer's silly superstition -- but John had a new routine for the remainder of his 26 seasons in the Majors. Whatever you call it, John working with his hands in the dirt did wonders for that sinker. (This writer's father was that inquisitive acquaintance, then a young law clerk assisting John's attorney, Bob Cohen.)

Which brings us, two decades later, to Brett Marshall, also a sinker-baller currently ranked as the Yankees' No. 20 prospect.

"I definitely understand that," Marshall said of John's pre-start tactic. "But I don't like to tire myself out. In the later innings my arm is kind of hanging and I know I have that sinker.

"When I slow it down a tick or two, I get a little bit more movement. The slower it is, the more it has to move from the pitcher's mound to home plate. The harder I throw it, the less time it has to move. At the beginning of the game, it's still a great pitch."

So no need for seeds and soil for this hurler. That's not all of Marshall's sinker story, however. When New York nabbed the Texas prep product with its sixth-round choice in the 2008 draft, its brass asked him to bag his best offering. The Yankees wanted the then-18-year-old to focus on developing his straight four-seam fastball, changeup and curveball. Four years later, he believes he put unnecessary stress on his elbow while learning that last offering.

"My first year, I threw a lot of curveballs. Every day, even after a start, I'd throw 100 curveballs on flat ground, just spinning 'em, trying to get a feel for it," he said. "So after Tommy John [surgery in 2009], I was like, 'Give me my sinker back. That's what I had when ya'll signed me, and that was one big thing that got me drafted.' I have been throwing it ever since."

And good luck arguing over the results. In his first run through the Eastern League with the Double-A Trenton Thunder this season, Marshall has won 10 of 13 decisions and compiled a 3.00 ERA. In one five-start stretch in May, the 22-year-old right-hander had four scoreless outings, each spanning at least six frames. Most importantly, he's stayed healthy, missing just one start in late June due to knee bursitis.

MiLB.com asked Marshall to describe and grade each of the four pitches he throws. (His grade is based on a scout's traditional 20-80 scale, 50 being the Major League average.) Here is Marshall, in his own words.

Pitch one: Two-seam fastball

Origin: I developed it back in Little League. When my dad first taught me how to pitch, he made me grab the ball two-seam style. Ever since then, I threw it. I was always a position player thought Little League and high school so I was always changing my arm slot and had a lot of movement on my ball. When I first got on the mound, it was just natural movement.

Purpose: I don't try to do too much with it because some days it will be moving so much that I can't really control it. Some days it will be flatter than others. Mainly, I just aim it down the middle and let it work and keep down in the zone and get a lot of ground balls off of it.

Grip: Fingers together between the two horseshoes.

Speed: Anywhere from 88 to 93 mph. I've gotten up to 94 this year.

Grade: 60-70.

Pitch two: Four-seam fastball

Purpose: If I am ahead in a count, 0-2, or just trying to throw a first-pitch strike, I'll throw it. Or maybe go up in the zone and make the batter chase it because it's a harder pitch and comes out firmer. It still has a little bit of run on it, but for the most part it stays straight.

Grip: Across the horseshoe.

Speed: 90 to 93, 94.

Grade: 60-70.

Pitch three: Changeup

Origin: I had it in high school. I didn't throw it much. My first year of pro ball, I threw it a little different, and I changed it up after Tommy John surgery to a circle-change. The one I was throwing before was like a three-finger changeup, and it was really hard -- like, I was throwing it 86 to 89 and I was like, 'I need to slow it down.' When I switched to the circle, it started coming out really well: a lot of depth on it, good fade.

Purpose: I put great arm speed on it to make it look like my fastball and get a lot of swings and misses on it.

Grip: I don't hold it tot hard, too light. I grip it two-seam style to get a little more run on it.

Speed: 80 to 83.

Grade: I would grade that one pretty high, between 70 and 80 because I've been told it's definitely a plus-plus, big-league changeup, so I'm really glad to have it.

Pitch four: Slider

Origin: I threw it in high school too. One of my select-team coaches -- he played in the big leagues for a few years -- taught me how to throw it. But after I signed, the Yankees took it away and gave me a curveball. It wasn't coming along the way we wanted to, so after Tommy John, they gave me my slider back. We were trying to take the stress off my elbow. It's gotten better in the last two years. (I'll also be developing the curveball; we're going to be bringing it back here, hopefully, in the next month or so. Being a starter, I want to have that second breaking ball as a show-me pitch. I've been throwing it on flat ground, playing catch and warming up. Some days, it comes out really well, and the next day, I can't even find how I was doing it.)

Purpose: Depends if I am trying to make them swing and miss 0-2, 1-2, throw the ball in the dirt or on a first pitch and just get it over for a strike and maybe make 'em hit it or ground it out. I am able to shorten it up a little bit, make it a little tighter, so it's coming out pretty firm right now.

Grip: I grab it just like the four-seam, but I tilt the ball more and put more pressure on my middle finger and hook my middle finger around the seam. I throw it just like a fastball and let the grip do the work.

Speed: It's been up to 86, 87 this year but usually stays 81 to 85.

Grade: It's been better more days than it is not, 60.

Andrew Pentis is a contributor to MLB.com. Follow him on Twitter at AndrewMiLB. This story was not subject to the approval of the National Association of Professional Baseball Leagues or its clubs.